The Environmental Protection Agency (EPA) has set, for 2007 and beyond, vehicle internal combustion engine emission requirements; one exemplary requirement for diesel engines, is NOx and non-methane hydrocarbons below 0.20 grams bhp-hr and 0.14 grams/bhp-hr, respectively. This contrasts with current standards of 4.0 grams/bhp-hr and 1.3 grams/bhp-hr, respectively. Thus, the catalytic converters must accomplish a significant reduction in NOx. There currently are no catalyst formulations which are able to adequately reach these restrictive standards; significant development will be required to reduce the cost and improve performance of new catalyst formulations. Apparatus that oxidizes engine fuel to provide a mix that enhances NOx reduction is disclosed in U.S. Pat. No. 5,412,946, in PCT published application WO 01/34950, and U.S. patent application Publication 2001/41153.
One known methodology for NOx reduction is the so-called SCR (Selective Catalytic Reduction) process, as shown in FIG. 1. Therein, a hydrocarbon-fueled engine 10 receives fuel from a tank 12 provided by a fuel pump 13, as well as air from a turbo compressor 14 in an air inlet line 15. An aqueous solution of urea is carried in a tank 16. The urea solution is applied to a hydrolysis unit 17 together with engine exhaust in a pipe 18, wherein heat of the exhaust converts the urea solution to gaseous ammonia. The ammonia then reacts in a selective catalytic converter 19 with NOx in the exhaust gas to convert the NOx to nitrogen and water, providing reduced NOx in the system exhaust 20. The problem is that there is no infrastructure in place to provide the urea solution at stations where fuel, particularly diesel fuel and gasoline, is obtained.
In commonly owned copending U.S. patent application Ser. No. 10/159,369 filed May 31, 2002, hydrogen for reducing NOx in catalytic converters or regenerating NOx trap adsorbents is generated utilizing moisture derived either directly or indirectly from engine exhaust. All of the aforementioned NOx reduction techniques are complicated and expensive.